CTS-XHP vs Elmax

bluntcut said:
Knife A & knife B, each chops a nail.

Knife A resulted with a 3 mm dent.
Knife B resulted with a 2 mm chip.

Which one is tougher?

For me - B is tougher because it has less damaged. Otoh in knife world, the answer might be 50/50 because pliable/ductile often marketed as tough. However, if knife B has a crack longer than 3mm or broke in half - Knife A is tougher.
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The degree of damage depth from cutting hard stuff like nail is not directly refer to toughness. Its combination of hardness(strength), toughness and the matrix construction of the material. Otherwise by your logic tungsten carbide would be considered to be tougher than copper which in reality it is not.

Toughness is resistance to breakage via stress or impact. If we want to make a appropriately comparison in toughness among steel we need comparable in hardness and properly grain structure. People can have a knife made of steel like L6 or 5160 at 57HRC and still being very brittle due to the lack of proper normalizing cycle after forging.
 
Deadboxhero already posted about toughness. I posted similar thing a couple years back. Knife A & B example was to point out - toughness in common sense is the same toughness in metallurgy.

There are common sense assumptions in knife A&B example, such as having 15dps edge bevel, edc behind edge thick, so on. A tungsten/ceramic knife won't survive the nail chopping impact.

True toughness of a knife is the sum of its parts - steel attributes, edge geometry, profile, handle, etc... Yeah, I like common sense way to look at thing. Toughness is the resistance to damage. YVMV.

shqxk said:
The degree of damage depth from cutting hard stuff like nail is not directly refer to toughness. Its combination of hardness(strength), toughness and the matrix construction of the material. Otherwise by your logic tungsten carbide would be considered to be tougher than copper which in reality it is not.

Toughness is resistance to breakage via stress or impact. If we want to make a appropriately comparison in toughness among steel we need comparable in hardness and properly grain structure. People can have a knife made of steel like L6 or 5160 at 57HRC and still being very brittle due to the lack of proper normalizing cycle after forging.
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This is the process used in the testing commissioned by Bohler Uddeholm:

ElmaxToughnessTest-1-s.jpg


Chuck
 
Thanks, Chuck. That's interesting information. Elmax is a great steel.

I take it that the weight or height of the swing was increased until the specimen broke?

Do you think a backyard testing system, such as swinging a cold chisel onto a 40-degree inclusive edge, gradually increasing the height of the dropped weight until chipping was observed -- would be a good way to test for toughness on our EDC's? I was thinking of having the chisel hit the edge at a 45-degree angle.
 
shqxk said:
Elmax is the most versatile super stainless steel period.

It is the toughest steel of all powdered stainless with excellent wear resistance. I would even preferred Elmax over M390 or S90V.

XHP is one of the best overall performance stainless steel but Elmax is just slightly better.
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Totally agree in every way
 
Twindog said:
I kind of disagree. Toughness is resistance to breaking, cracking or chipping, whether from impact or pressure. Strength is resistance to rolling or bending (beyond the yield point). Strength is highly correlated to hardness.

Edge stability is a blend of toughness, strength and wear resistance.
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Yes, this is my understanding also.
 
bluntcut said:
Knife A & knife B, each chops a nail.

Knife A resulted with a 3 mm dent.
Knife B resulted with a 2 mm chip.

Which one is tougher?

For me - B is tougher because it has less damaged. Otoh in knife world, the answer might be 50/50 because pliable/ductile often marketed as tough. However, if knife B has a crack longer than 3mm or broke in half - Knife A is tougher.
Click to expand...

Given the same impact on the same or identical nails with identical edge geometries for A and B, A is tougher because the failure mode is deformation. The failure mode for B is fracture.
 
Going into a ring to duke out with a robot. Fighter A came out with 3 teeth missing, while fighter B came out with 2 teeth missing. Which fighter is tougher ;)
LuckyC said:
Given the same impact on the same or identical nails with identical edge geometries for A and B, A is tougher because the failure mode is deformation. The failure mode for B is fracture.
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bluntcut said:
Going into a ring to duke out with a robot. Fighter A came out with 3 teeth missing, while fighter B came out with 2 teeth missing. Which fighter is tougher ;)
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Well, like my boss always used to say, It takes a big dog to weigh a ton. :)
Peace Brother.

Next to the last knife I bought was an Enzo Trapper 115 in Elmax. With more C than D2 and as much Ch as 440C at anywhere near Rc60, I'd expect it to be chippy as hades, but I've seen videos of guys batoning with a 95 in Elmax. I haven't done that (and most likely won't) but I do like the knife.
 
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fwiw since I could mis-interpreted toughness. So toughness to me

Tough describes resistance against a shape being alter. Translated to - a toughness of a blade/edge is level of resistance from being damage. Many of the blade/steel attributes are sub-set of toughness. e.g.

charpy impact test (aka impact toughness - interesting way to call it): Resistance/tough against fracture up to certain load by impact (avg max load). However this doesn't tell you whether the specimen can handles 2 impacts each at 1/2 load.

wear resistance: toughness against slow gradual loss from various causes, such as: abrasion, friction, rolling, fatigue, particle blasting, etc..

strength: resistance against movement and displacement.

corrosion resistance: toughness against chemistry changes.

etc..

Whereas ductility/pliable/move/adaptable of s solid material describes level of movement/displacement/compacting/etc this material supports/behaves. In essence, this behavior could contribute to toughness but not the other way around.
 
Larrin has established a theory framework for explaining toughness and it's correlation with carbide size and volume. That theory worked great on many steel types that he tested so I tend to believe in it. According to the micrograph of Elmax, it looks quite similar to XHP, so even though Larrin didn't test Elmax's toughness, I would expect Elmax's toughness to be similar to XHP, and may not be better than CPM-154. However, I am yet to see Larrin's test on it to make the argument.

For comparison of XHP and Elmax, I will definitely pick Elmax. Data from different sources have suggested that edge retention of Elmax and XHP are at similar level, while Elmax is much more corrosion resistant than XHP. I would expect Elmax to be similar to S30v/S35vn on both edge retention and corrosion resistance.

Currently for stainless steels, the toughness and edge retention seem to contradict with each other, if Elmax is really tougher than CPM-154, then that is great news as that means the boundary of edge retention/toughness line has been push further for stainless steels.
 
jdm61 said:
Number of high end kitchen knife makers used to use CPM 154 until many in that "industry" switched over to higher hardness AEB-L.
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With the resurgence in popularity of AEB-L as knifemakers have developed high-hardness heat treats for it and been able to get it in thicker stock, I wonder if we'll see Crucible do a PM AEB-L. Bet that'd be a real sweet option for people wanting stainless fixed blades without compromising on toughness as much.
 
madcap_magician said:
With the resurgence in popularity of AEB-L as knifemakers have developed high-hardness heat treats for it and been able to get it in thicker stock, I wonder if we'll see Crucible do a PM AEB-L. Bet that'd be a real sweet option for people wanting stainless fixed blades without compromising on toughness as much.
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PM AEB-L is pointless.

It is already finer than all the PM stainless steels.

The PM process shrinks carbides.

If there is little carbide volume than it doesn't do anything to improve.

The iron grains grow and shrink with HT not PM process.

The maker is in control of that.
 
It doesn't work that simply though, while the Carbides play a big role they are balanced by the other constituents that make up the Microstructure such as tempered martensite, retained austenite, grain size. Each of these things have elaborate detail to them alone. When they work in concert it is very complex and its interesting to see that sometimes one factor overrides the other at times or can cha ge the behaviour.
I'd say don't get tunnel vision on just carbides alone.

Vanax has the finest particle size of the PM stainless at that volume yet is not the toughest on charpy impact toughness testing.

But one can argue in real world those finer Nitrides go a long way with improving the edge Stability of the knife in use.

superpog said:
Larrin has established a theory framework for explaining toughness and it's correlation with carbide size and volume. That theory worked great on many steel types that he tested so I tend to believe in it. According to the micrograph of Elmax, it looks quite similar to XHP, so even though Larrin didn't test Elmax's toughness, I would expect Elmax's toughness to be similar to XHP, and may not be better than CPM-154. However, I am yet to see Larrin's test on it to make the argument.

For comparison of XHP and Elmax, I will definitely pick Elmax. Data from different sources have suggested that edge retention of Elmax and XHP are at similar level, while Elmax is much more corrosion resistant than XHP. I would expect Elmax to be similar to S30v/S35vn on both edge retention and corrosion resistance.

Currently for stainless steels, the toughness and edge retention seem to contradict with each other, if Elmax is really tougher than CPM-154, then that is great news as that means the boundary of edge retention/toughness line has been push further for stainless steels.
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